import java.util.ArrayList;

/**
 * Created with IntelliJ IDEA.
 * Description:
 * User: ${USER}
 * Date: ${YEAR}-${MONTH}-${DAY}
 * Time: ${TIME}
 */
public class Main {
    ArrayList
    public static void main(String[] args) {
        System.out.println("Hello world!");
    }
}class Solution {
    public String tree2str(TreeNode root) {
        if (root == null) {
            return "";
        }
        if (root.left == null && root.right == null) {
            return Integer.toString(root.val);
        }
        if (root.right == null) {
            return new StringBuffer().append(root.val).append("(").append(tree2str(root.left)).append(")").toString();
        }
        return new StringBuffer().append(root.val).append("(").append(tree2str(root.left)).append(")(").append(tree2str(root.right)).append(")").toString();
    }
}
